1. Field of the Invention
The present invention relates to a belt type continuously variable transmission in which a metal belt is wound around a drive pulley and a driven pulley.
2. Description of Related Art
In recent years, under circumstances of increasing demand for environmentally friendly automobiles, a belt type continuously variable transmission that uses a metal belt has attracted attention as a transmission that is capable of reducing fuel consumption while simultaneously improving running performance. The belt type continuously variable transmission provides a relatively smooth acceleration without shift-shock, is relatively quiet in terms of running performance, and achieves lower fuel consumption compared to an automatic transmission by integral control of the transmission and an engine that maintains engine rotational speed with relatively high combustion efficiency in terms of fuel consumption. There is an increasing need for additional increased torque transmission capacity of the belt type continuously variable transmission to enhance multi-purpose features that enable application to various types of vehicles.
Conventionally, as disclosed in Japanese Patent Application Laid-open No. 52-47158, the saddle faces of the metal elements are made into a convex shape (i.e., crowning) to center the metal ring assembly on the saddle faces in order to prevent deterioration of durability from the edges of the metal ring assembly moving on the saddle faces of the metal elements contacting the neck parts of the metal elements and V-faces of pulleys.
However, even if the saddle faces of the metal elements are configured to have a convex shape so as to perform the centering function, the metal ring assembly inevitably moves on the saddle faces under certain operating conditions of the belt type continuously variable transmission. As one of the causes, it has been found that the movement of the metal ring assembly is greatly influenced by the ratio of the flexural stiffness of the movable pulley half compared to that of the fixed pulley half of the drive pulley.